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@INPROCEEDINGS{Samsun:1052330,
author = {Samsun, Remzi Can and Frömling, Till and Gross-Barsnick,
Sonja-Michaela and Kadyk, Thomas and Schulze-Küppers, Falk
and Lenser, Christian and Margaritis, Nikolaos and Menzler,
Norbert H. and Naumenko, Dmitry and Schäfer, Dominik and
Uecker, Jan and Vibhu, Vaibhav and Zhang, Shidong},
title = {{S}olid {O}xide {E}lectrolysis and {F}uel {C}ells at
{F}orschungszentrum {J}ülich: {A}n {O}verview and {R}ecent
{A}dvances},
volume = {MA2025-03},
number = {1},
reportid = {FZJ-2026-00938},
series = {Meeting abstracts},
pages = {39 - 39},
year = {2025},
abstract = {Solid Oxide Cell (SOC) technology is currently experiencing
a high level of interest, as the capabilities and the
potential of the technology are well aligned with the global
efforts to achieve zero emissions. Forschungszentrum Jülich
has been heavily involved in the SOC research for more than
three decades and has become a cornerstone of the global SOC
research community. Selected historical highlights of this
research include Jülich’s contributions to the
development of the fuel electrode-supported design with
material innovations and the advancement of the design for
scalability in cells and stacks [1, 2], the development of
the Crofer 22 APU alloy in close cooperation with industrial
partners [3, 4] and the long-term operation of a short stack
in fuel cell mode for more than 100,000 hours [5]. Today,
the SOC research at Jülich is organized in five institutes
and is characterized by a multidisciplinary approach to
solving current fundamental and applied challenges in order
to further develop the technology for various application
areas. This comprehensive approach covers all aspects from
materials to systems, including synthesis, fabrication,
modeling, testing, demonstration, and post-test analysis.
This contribution provides a general overview of these
activities addressing current research topics and recent
advances.Sustainability $\&$ cost reductionMaking SOC
technology more economically attractive is an important
goal, which can be achieved in different ways. One approach
is to use cheaper steel grades, e.g. DIN1.4509 or DIN1.4016
that were not originally optimized for SOC application, but
whose performance could be improved by coatings retaining
Cr-evaporation. As part of a European project, long-term
oxidation studies were carried out on coated steels [6],
revealing excellent adhesion and microstructure stability of
the coating systems. In addition, new coatings based on
Mn-Co-Fe or Mn-Cu-Fe-spinels applied by electrophoresis
(EPD) have been developed. EPD could be a more sustainable
alternative to plasma spraying, especially suitable for
thin-film cassette-type interconnects. Scale-up to real
stack sizes and comparison with wet powder spraying [7] are
currently underway.Another way to reduce costs is to
minimize efforts to purify reactants (water, air, etc.). For
this case the effect of pollutants such as Cl or S on the
microstructure and properties of the cell components has
been studied [8], revealing important degradation
mechanisms. Cell degradation studies can be complemented
with recently developed FIB/SEM and X-ray computed
tomography [9]. Furthermore, approaches for the recycling of
SOC metallic constituents have been developed with the aim
of producing different Cr- and Ni-containing stainless steel
grades, supported by thermodynamic modeling [10].A recycling
strategy for operated stacks and especially also for the
cell fraction has been implemented in a large German funded
$R\&D$ project [11, 12]. The developed cell recycling route
starts with a reoxidation step of the metallic Ni, the
acidic leaching of the air electrode and the remaining
contact layer material. The resulting fraction then consists
of NiO, 8YSZ and remnants from GDC. This material mixture
could then be post-processed (milling) and re-dispersed into
a tape casting slurry for the fuel support up to amounts of
$50\%$ of recyclate. Full cells were fabricated and showed
similar performance to the state-of-the-art fuel-electrode
supported cells. The leached fraction could be separated
into La-phase and a residual phase. The La could be
re-processed. The ongoing work focuses on the remaining
leached fraction.Cell development $\&$ modelingExtensive
studies of long-term SOC operation and degradation at
Jülich show that a ceramic material substitution is
necessary to achieve a long lifetime of the SOC technology.
The efforts include the development of proton conducting
ceramic cells [13] and new electrode materials for oxygen
conducting ceramics [14]. Finally, the driving force is to
lower the application temperature to reduce the impact of
degradation mechanisms.Since Ni-YSZ cermets have shown high
degradation rates in steam electrolysis due to Ni migration,
there is a strong focus on replacing Ni-YSZ in fuel
electrode-supported cells. To enable a Ni-GDC cermet
electrode, a three-layer electrolyte (GDC-YSZ-GDC) has been
developed using a combination of screen-printing and
magnetron sputtering. Excellent cell/stack performance can
be achieved by avoiding interdiffusion between YSZ and GDC
at the electrode/electrolyte interface, but cell processing
needs to be optimized. Other efforts to replace Ni-YSZ
include the development of an all-ceramic electrode made of
SrTi0.5Fe0.5O3-d (STF), and the development of perovskite
oxides with exsolved Ni particles.To gain a fundamental
understanding of the degradation of electrode structures, a
hierarchical model was developed that relates changes at the
level of electrode particles to the evolution of the
electrode structure and resulting material properties, and
ultimately to the overall lifetime performance. In the fuel
electrode, it was found that the limited ion conduction
leads to a locally enhanced degradation rate close to the
electrolyte side, until the breakdown of the percolating
nickel particle network and thus of the electron
conductivity is reached, resulting in a movement of the
degradation zone deeper into the electrode. This creates a
moving degradation front at the microstructural level, which
leaves a fingerprint in the electrochemical impedance
spectra. Overall, the model can be easily modified and
extended (e.g. by including Ni migration). Since its
computational time is low, it could be used as a concomitant
analyzing tool during the operation of the SOC.Another
challenge that is being addressed is the impact of different
fuel sources (ammonia, biogas and their impurities) [15] on
the functional properties and lifetime of fuel cells.
Similarly, different types of components (e.g. sodium
chloride) in water sources can affect the application of
solid oxide electrolyzers. As access to high purity water is
an issue and electrolysis should not contribute to further
depletion of drinking water sources, the development of
wastewater or saltwater electrolysis is an important
sustainability goal for the hydrogen economy.Stack
technology $\&$ characterizationOne of the 20-layer stacks
assembled with the prospect of being used in the rSOC system
showed a short circuit after the initial joining process and
cell reduction. To avoid the disposal of the stack,
dismantling was carried out level by level for six repeating
units until the damaged layer could be removed. A green foil
of the glass-based composite sealant was placed on the
residuals of the broken joint and a second joining process
was performed against a new top plate. After this repair
process, the stack operation could be started with promising
results.In the field of electrochemical stack
characterization, the research focuses on the development of
innovative measurement and analysis techniques. Fiber optic
sensors are used for precise and compact temperature
measurements under highly dynamic SOC operating conditions.
A combined approach using electrochemical impedance
spectroscopy (EIS) and total harmonic distortion provides
detailed insight into the performance of a co-electrolysis
stack. A novel data-driven methodology was developed using
2,600 EIS measurements from SOC stacks operated in various
modes for over 47,000 hours. This method allows
reconstruction of the EIS from sparse frequency sampling
[16]. Long-term degradation effects are studied in a
multi-stack configuration consisting of six sub-stacks
operated under co-electrolysis conditions, revealing the
effect of operating time with a common history of all
samples. Additional degradation analysis focuses on one
stack under steam electrolysis at reduced temperatures, with
variations in current density and feed gas composition over
four 1,000-hour phases. Modeling efforts include a CFD-based
sulfur poisoning analysis of the co-electrolysis and a
predictive performance evaluation method coupling phase
field modeling with CFD. At the system level, the rSOC
system design in the 10/40 kW power class demonstrated
reliable operation for over 11,500 h at temperature, with
ongoing optimization of control strategies for cyclic
operation and realistic load profiles. A digital twin of the
integrated module of the rSOC system, developed using
OpenFOAM, was validated and supports fast, accurate
characterization.Post-test analysisPost-test analyses
provide critical insight into failure modes and degradation
processes, including electrical behavior, material
interactions, and operational influences. Failure mechanisms
such as short circuits, leakage, and external factors are
characterized alongside degradation phenomena such as
chromium poisoning and sealant degradation. Key operating
parameters such as temperature, current density, and fuel
composition, are evaluated for their impact on performance
and material stability. An SOC-stack autopsy methodology has
been developed that demonstrates the disassembly of a module
for the subsequent post-test analysis.The Jülich long-term
test in fuel cell operation, which lasted about 10 years,
was investigated immediately after the end of the test [17,
18]. The results showed relatively few changes, interactions
or damage considering the long operating time. One of the
main conclusions was that the interface between the LSCF air
electrode and the GDC barrier layer was somewhat changed.
Secondary phase formation was observed, leading to tiny
nanocrystals and partial incorporation of Cr into the LSCF
grains. The secondary formed crystals were also found in the
pores of the GDC layer. Additional advanced characterization
tools such as Raman spectroscopy and µ-Laue diffraction
revealed similar results compared to the SEM
characterizations. However, one simple question remained
unanswered. None of the techniques applied could verify or
falsify whether the LSCF perovskite was still a perovskite
or had transformed into another crystal structure after such
a long time. Thus, additional high-resolution TEM
investigations were performed. Finally, it was proven that
the entire air-electrode volume, from the interface to the
GDC to the bulk layer, is still a perovskite. This result
proves the chemical stability of the perovskite structure.},
month = {Jul},
date = {2025-07-14},
organization = {SOFC: 19th International Symposium on
Solid Oxide Fuel Cells (SOFC-XIX),
Stockholm (Sweden), 14 Jul 2025 - 18
Jul 2025},
cin = {IET-1 / ITE / IET-3 / IMD-2 / IMD-1},
cid = {I:(DE-Juel1)IET-1-20110218 / I:(DE-Juel1)ITE-20250108 /
I:(DE-Juel1)IET-3-20190226 / I:(DE-Juel1)IMD-2-20101013 /
I:(DE-Juel1)IMD-1-20101013},
pnm = {1231 - Electrochemistry for Hydrogen (POF4-123) /
Verbundvorhaben $SOC-Degradation_2$ ' Teilvorhaben A
(03SF0621A) / PHOENIX - Verbundvorhaben PHOENIX: Im Fokus
des Launch Space Power-to-X (PHOENIX) steht die
Weiterentwicklung und Demonstration der vielversprechendsten
P2X-Technologien. Der Forschungs- und Entwicklungsbedarf zur
Realisierung nachhaltiger P2X-Technologien konzentriert sich
auf die Elektrolyse als Schlüsseltechnologie
(MWIDE-03SF0775A) / iNEW2.0 - Verbundvorhaben iNEW2.0: Im
Zentrum des Inkubators Nachhaltige Elektrochemische
Wertschöpfungsketten (iNEW 2.0) steht die Erforschung und
Entwicklung neuartiger und leistungsfähiger
Elektrolyse-verfahren zur Anwendung in nachhaltigen
Power-to-X (P2X) Wertschöpfungsketten. (BMBF-03SF0627A) /
MacGyver - Verbundvorahben MacGyver: Materialien und
Konzepte für einen grünen Wasserstoffvektor
(BMBF-03SF0785A) / PRELUDE - Verbundvorhaben PRELUDE:
Prozess- und Meerwasser-Elektrolyse für eine
umweltverträgliche Grüne Wasserstoffwirtschaft in
Deutschland (BMBF-03SF0650A) / BMBF-03SF0716A -
Verbundvorhaben DryHy: Wasserbewusste Erzeugung von
Wasserstoff und e-Fuels in trockenen Regionen (Phase 1),
Teilvorhaben: Vorbereitung der Demonstationsphase durch
Untersuchung und Entwicklung der Einzeltechnologien
(BMBF-03SF0716) / NOUVEAU - NOVEL ELECTRODE COATINGS AND
INTERCONNECT FOR SUSTAINABLE AND REUSABLE SOEC (101058784) /
SOFC - Solid Oxide Fuel Cell (SOFC-20140602)},
pid = {G:(DE-HGF)POF4-1231 / G:(BMBF)03SF0621A /
G:(DE-Juel1)MWIDE-03SF0775A / G:(DE-Juel1)BMBF-03SF0627A /
G:(DE-Juel1)BMBF-03SF0785A / G:(DE-Juel1)BMBF-03SF0650A /
G:(DE-Juel1)BMBF-03SF0716 / G:(EU-Grant)101058784 /
G:(DE-Juel1)SOFC-20140602},
typ = {PUB:(DE-HGF)8 / PUB:(DE-HGF)7},
doi = {10.1149/MA2025-03139mtgabs},
url = {https://juser.fz-juelich.de/record/1052330},
}
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